/*
 * ====================================================================
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 */

package com.feilong.lib.org.apache.http.protocol;

import java.io.IOException;

import com.feilong.lib.org.apache.http.ConnectionReuseStrategy;
import com.feilong.lib.org.apache.http.HttpEntity;
import com.feilong.lib.org.apache.http.HttpEntityEnclosingRequest;
import com.feilong.lib.org.apache.http.HttpException;
import com.feilong.lib.org.apache.http.HttpRequest;
import com.feilong.lib.org.apache.http.HttpResponse;
import com.feilong.lib.org.apache.http.HttpResponseFactory;
import com.feilong.lib.org.apache.http.HttpServerConnection;
import com.feilong.lib.org.apache.http.HttpStatus;
import com.feilong.lib.org.apache.http.HttpVersion;
import com.feilong.lib.org.apache.http.MethodNotSupportedException;
import com.feilong.lib.org.apache.http.ProtocolException;
import com.feilong.lib.org.apache.http.UnsupportedHttpVersionException;
import com.feilong.lib.org.apache.http.annotation.Contract;
import com.feilong.lib.org.apache.http.annotation.ThreadingBehavior;
import com.feilong.lib.org.apache.http.entity.ByteArrayEntity;
import com.feilong.lib.org.apache.http.impl.DefaultConnectionReuseStrategy;
import com.feilong.lib.org.apache.http.impl.DefaultHttpResponseFactory;
import com.feilong.lib.org.apache.http.util.Args;
import com.feilong.lib.org.apache.http.util.EncodingUtils;
import com.feilong.lib.org.apache.http.util.EntityUtils;

/**
 * {@code HttpService} is a server side HTTP protocol handler based on
 * the classic (blocking) I/O model.
 * <p>
 * {@code HttpService} relies on {@link HttpProcessor} to generate mandatory
 * protocol headers for all outgoing messages and apply common, cross-cutting
 * message transformations to all incoming and outgoing messages, whereas
 * individual {@link HttpRequestHandler}s are expected to implement
 * application specific content generation and processing.
 * <p>
 * {@code HttpService} uses {@link HttpRequestHandlerMapper} to map
 * matching request handler for a particular request URI of an incoming HTTP
 * request.
 * <p>
 * {@code HttpService} can use optional {@link HttpExpectationVerifier}
 * to ensure that incoming requests meet server's expectations.
 *
 * @since 4.0
 */
@Contract(threading = ThreadingBehavior.IMMUTABLE_CONDITIONAL)
public class HttpService{

    private volatile HttpProcessor            processor           = null;

    private volatile HttpRequestHandlerMapper handlerMapper       = null;

    private volatile ConnectionReuseStrategy  connStrategy        = null;

    private volatile HttpResponseFactory      responseFactory     = null;

    private volatile HttpExpectationVerifier  expectationVerifier = null;

    /**
     * Create a new HTTP service.
     *
     * @param processor
     *            the processor to use on requests and responses
     * @param connStrategy
     *            the connection reuse strategy. If {@code null}
     *            {@link DefaultConnectionReuseStrategy#INSTANCE} will be used.
     * @param responseFactory
     *            the response factory. If {@code null}
     *            {@link DefaultHttpResponseFactory#INSTANCE} will be used.
     * @param handlerMapper
     *            the handler mapper. May be null.
     * @param expectationVerifier
     *            the expectation verifier. May be null.
     *
     * @since 4.3
     */
    public HttpService(final HttpProcessor processor, final ConnectionReuseStrategy connStrategy, final HttpResponseFactory responseFactory,
                    final HttpRequestHandlerMapper handlerMapper, final HttpExpectationVerifier expectationVerifier){
        super();
        this.processor = Args.notNull(processor, "HTTP processor");
        this.connStrategy = connStrategy != null ? connStrategy : DefaultConnectionReuseStrategy.INSTANCE;
        this.responseFactory = responseFactory != null ? responseFactory : DefaultHttpResponseFactory.INSTANCE;
        this.handlerMapper = handlerMapper;
        this.expectationVerifier = expectationVerifier;
    }

    /**
     * Create a new HTTP service.
     *
     * @param processor
     *            the processor to use on requests and responses
     * @param connStrategy
     *            the connection reuse strategy. If {@code null}
     *            {@link DefaultConnectionReuseStrategy#INSTANCE} will be used.
     * @param responseFactory
     *            the response factory. If {@code null}
     *            {@link DefaultHttpResponseFactory#INSTANCE} will be used.
     * @param handlerMapper
     *            the handler mapper. May be null.
     *
     * @since 4.3
     */
    public HttpService(final HttpProcessor processor, final ConnectionReuseStrategy connStrategy, final HttpResponseFactory responseFactory,
                    final HttpRequestHandlerMapper handlerMapper){
        this(processor, connStrategy, responseFactory, handlerMapper, null);
    }

    /**
     * Create a new HTTP service.
     *
     * @param processor
     *            the processor to use on requests and responses
     * @param handlerMapper
     *            the handler mapper. May be null.
     *
     * @since 4.3
     */
    public HttpService(final HttpProcessor processor, final HttpRequestHandlerMapper handlerMapper){
        this(processor, null, null, handlerMapper, null);
    }

    /**
     * Handles receives one HTTP request over the given connection within the
     * given execution context and sends a response back to the client.
     *
     * @param conn
     *            the active connection to the client
     * @param context
     *            the actual execution context.
     * @throws IOException
     *             in case of an I/O error.
     * @throws HttpException
     *             in case of HTTP protocol violation or a processing
     *             problem.
     */
    public void handleRequest(final HttpServerConnection conn,final HttpContext context) throws IOException,HttpException{

        context.setAttribute(HttpCoreContext.HTTP_CONNECTION, conn);

        HttpRequest request = null;
        HttpResponse response = null;

        try{
            request = conn.receiveRequestHeader();
            if (request instanceof HttpEntityEnclosingRequest){

                if (((HttpEntityEnclosingRequest) request).expectContinue()){
                    response = this.responseFactory.newHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_CONTINUE, context);
                    if (this.expectationVerifier != null){
                        try{
                            this.expectationVerifier.verify(request, response, context);
                        }catch (final HttpException ex){
                            response = this.responseFactory
                                            .newHttpResponse(HttpVersion.HTTP_1_0, HttpStatus.SC_INTERNAL_SERVER_ERROR, context);
                            handleException(ex, response);
                        }
                    }
                    if (response.getStatusLine().getStatusCode() < 200){
                        // Send 1xx response indicating the server expections
                        // have been met
                        conn.sendResponseHeader(response);
                        conn.flush();
                        response = null;
                        conn.receiveRequestEntity((HttpEntityEnclosingRequest) request);
                    }
                }else{
                    conn.receiveRequestEntity((HttpEntityEnclosingRequest) request);
                }
            }

            context.setAttribute(HttpCoreContext.HTTP_REQUEST, request);

            if (response == null){
                response = this.responseFactory.newHttpResponse(HttpVersion.HTTP_1_1, HttpStatus.SC_OK, context);
                this.processor.process(request, context);
                doService(request, response, context);
            }

            // Make sure the request content is fully consumed
            if (request instanceof HttpEntityEnclosingRequest){
                final HttpEntity entity = ((HttpEntityEnclosingRequest) request).getEntity();
                EntityUtils.consume(entity);
            }

        }catch (final HttpException ex){
            response = this.responseFactory.newHttpResponse(HttpVersion.HTTP_1_0, HttpStatus.SC_INTERNAL_SERVER_ERROR, context);
            handleException(ex, response);
        }

        context.setAttribute(HttpCoreContext.HTTP_RESPONSE, response);

        this.processor.process(response, context);
        conn.sendResponseHeader(response);
        if (canResponseHaveBody(request, response)){
            conn.sendResponseEntity(response);
        }
        conn.flush();

        if (!this.connStrategy.keepAlive(response, context)){
            conn.close();
        }
    }

    private boolean canResponseHaveBody(final HttpRequest request,final HttpResponse response){
        if (request != null && "HEAD".equalsIgnoreCase(request.getRequestLine().getMethod())){
            return false;
        }
        final int status = response.getStatusLine().getStatusCode();
        return status >= HttpStatus.SC_OK && status != HttpStatus.SC_NO_CONTENT && status != HttpStatus.SC_NOT_MODIFIED
                        && status != HttpStatus.SC_RESET_CONTENT;
    }

    /**
     * Handles the given exception and generates an HTTP response to be sent
     * back to the client to inform about the exceptional condition encountered
     * in the course of the request processing.
     *
     * @param ex
     *            the exception.
     * @param response
     *            the HTTP response.
     */
    protected void handleException(final HttpException ex,final HttpResponse response){
        if (ex instanceof MethodNotSupportedException){
            response.setStatusCode(HttpStatus.SC_NOT_IMPLEMENTED);
        }else if (ex instanceof UnsupportedHttpVersionException){
            response.setStatusCode(HttpStatus.SC_HTTP_VERSION_NOT_SUPPORTED);
        }else if (ex instanceof ProtocolException){
            response.setStatusCode(HttpStatus.SC_BAD_REQUEST);
        }else{
            response.setStatusCode(HttpStatus.SC_INTERNAL_SERVER_ERROR);
        }
        String message = ex.getMessage();
        if (message == null){
            message = ex.toString();
        }
        final byte[] msg = EncodingUtils.getAsciiBytes(message);
        final ByteArrayEntity entity = new ByteArrayEntity(msg);
        entity.setContentType("text/plain; charset=US-ASCII");
        response.setEntity(entity);
    }

    /**
     * The default implementation of this method attempts to resolve an
     * {@link HttpRequestHandler} for the request URI of the given request
     * and, if found, executes its
     * {@link HttpRequestHandler#handle(HttpRequest, HttpResponse, HttpContext)}
     * method.
     * <p>
     * Super-classes can override this method in order to provide a custom
     * implementation of the request processing logic.
     *
     * @param request
     *            the HTTP request.
     * @param response
     *            the HTTP response.
     * @param context
     *            the execution context.
     * @throws IOException
     *             in case of an I/O error.
     * @throws HttpException
     *             in case of HTTP protocol violation or a processing
     *             problem.
     */
    protected void doService(final HttpRequest request,final HttpResponse response,final HttpContext context)
                    throws HttpException,IOException{
        HttpRequestHandler handler = null;
        if (this.handlerMapper != null){
            handler = this.handlerMapper.lookup(request);
        }
        if (handler != null){
            handler.handle(request, response, context);
        }else{
            response.setStatusCode(HttpStatus.SC_NOT_IMPLEMENTED);
        }
    }

}
